A method of the kind described above is disclosed, for example, in U.S. Pat. No. 5,632,883. The application of periodic pump current pulses to the measurement and reference electrodes affords the advantage that, in this way, two switching states occur. In the first state, the current source is coupled to the concentration cell and, in the second state, the current source is decoupled from the concentration cell so that the voltage, which serves as the measurement signal, between the measurement and reference electrode is not influenced by the current source in the decoupled state. In this way, a disturbance of the measurement signal because of the in-coupling of the current is eliminated. This in-coupling of the current leads to an additive voltage component of the measurement signal which, in turn, defines a disturbance of the measurement signal because of the temperature dependency of the internal resistance of the solid electrolyte.
In such a method and arrangement for detecting the oxygen content in a gas, it is problematic that, for a clocked pump reference, the reference pump current must be selected higher than for a non-clocked pump reference in order to obtain, over a time average, an adequate oxygen partial pressure in the concentration cell.
This leads to the situation that intense polarization effects occur on the concentration cell because of the higher pump current especially in the cold state of the concentration cell. Therefore, the actual sensor signal is made incorrect because of the polarization effects. Additive voltage components on the actual measurement signal occur because of the polarization effects. These voltage components lead to a signal shift which is present even after the pump current pulses.